1988 JEEP CHEROKEE lock

and cruise control remains inoperative, perform following
adjustments to determine if control module is functional.
1) Remove control module attaching screws or tie straps and
move control module downward for adjustment access. Turn centering
adjustment screw to 10 o'clock position. Turn low speed adjustment
screw to 10 o'clock position. Turn sensitivity adjustment screw fully
clockwise.
CAUTION: Adjustment potentiometers are extremely delicate. Carefully
insert screwdriver and do not push or turn screws
excessively hard. Maximum movement is 3/4 turn.
2) Adjustments are not precisely correct for vehicle, but are
acceptable to determine if control module is functioning. Perform
precise adjustments by road testing vehicle on level road. If
adjustments have no effect on cruise control, replace control module.
3) If actual engagement speed is 2 MPH or more above selected
speed, stop vehicle and turn centering screw 1/16 of a turn
counterclockwise. Recheck engagement speed and adjust as necessary.
4) If engagement speed is 2 MPH or more below selected speed,
turn centering screw 1/16 of a turn clockwise. Recheck engagement
speed and adjust as necessary.
Fig. 2: Control Module Adjustment Screws
Courtesy of Chrysler Motors.
VACUUM VENT VALVE
Depress brake or clutch pedal and hold in depressed position.
Move vacuum vent valve toward bracket on pedal as far as possible.
Release brake or clutch pedal.
TESTING
NOTE: Vehicles with computerized engine controls, should be tested
for stored computer codes. Codes and related problems must
be repaired prior to cruise control diagnosis and repair.
For additional information, see COMPUTERIZED ENGINE CONTROLS
section.
PRELIMINARY INSPECTION
Ensure cruise control wire harness is properly connected to

control module before starting diagnosis or repair procedure, as this
connection is disturbed when Cruise Command System Tester (AM PC-1-R)
is used. Poor connection at this point may be improperly diagnosed as
control module malfunction.
Brake light and clutch switches should be properly adjusted.
Ensure that all vacuum lines are correctly routed and tightly
connected.
CRUISE COMMAND SYSTEM TESTS
Testing is performed with Cruise Command System Tester (AM
PC-1-R). Remove wire harness connector from control module. Connect
tester to wire harness connector. Perform tests as part of service
diagnosis to determine cause and correction of system malfunction.
Various tester lights are associated with specific components,
circuits, etc.
CONTROL SWITCH CONTINUITY
Wrangler
NOTE: Voltage checks should show battery voltage. If resistance
readings are incorrect, check circuit for an open or a
short. Cruise control module terminal No. 1 grounds through
connector at engine block.
Light No. 1 "OFF" (Set Switch)
With control switch in "ON" position, check for battery
voltage between HAZ/STOP and in-line fuse, terminal No. 14 and ground
terminal No. 1
Light No. 2 "OFF" (Control Switch & Speed Sensor)
With control switch in "ON" position, check for battery
voltage between HAZ/STOP and in-line fuse, terminal No. 5 and ground
terminal No. 1. With ignition switch in "OFF" position, check
resistance between terminals No. 2 and No. 3. Resistance should be 15-
50 ohms.
Light No. 3 "OFF" (Brake Light Ground)
With ignition switch in "ON" position, install jumper wire
between terminals No. 7 and No. 13. If brake lights do not turn on,
check fuses and brake light switch connections.
Light No. 4 "OFF" (Throttle Position Feedback Sensor)
With ignition switch in "ON" position, check for battery
voltage between gauge fuses at terminals No. 7 and No. 1.
With ignition switch in "OFF" position, check resistance
between terminals No. 2 and No. 11. Resistance should be 2400-4000
ohms. At idle resistance should be 2800-4300 ohms and at wide open
throttle resistance should be 4000 ohms.
Light No. 5 "OFF" (Resume/Accel/Vent Valve)
With control switch in "RESUME/ACCEL" position, check for
battery voltage between HAZ/STOP and in-line fuse, terminal No. 10 and
ground terminal No. 1. With ignition switch in "OFF" position, check
resistance between terminals No. 6 and No. 12. Resistance should be
30-50 ohms. Resistance between terminals No. 6 and ground, and
terminal No. 12 and ground should be infinite (open).
Light No. 6 "OFF" (Resume/Accel/Charge Valve)
With control switch in "RESUME/ACCEL" position, check for
battery voltage between HAZ/STOP and in-line fuse, terminal No. 10 and
ground terminal No. 1. With ignition switch in "OFF" position, check
resistance between terminals No. 4 and No. 12. Resistance should be

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DEFO GGER - R EA R W IN DO W

1988 J e ep C hero ke e
1988 Defoggers
REAR WINDOW
Jeep: All Models
DESCRIPTION & OPERATION
System consists of 2 vertical bus bars and horizontal rows of
heating elements fused to inside of glass, a control switch, an
indicator light, and timer relay.
The grid feed wire is connected to bus bar on driver's side
of window. Ground bus bar is on right side of vehicle. Timer/relay
receives current from fuse block. A circuit breaker protects defogger
circuit.
NOTE: On some Jeep models, defogger switch and electric tailgate
switch are serviced as an assembly.
TROUBLE SHOOTING
NOTE: Control switch testing is not available for Wrangler models.
1) On Cherokee, Comanche and Wagoneer models, turn ignition
switch to "ON" position. Check for current at "I" and "B" terminals.
See Fig. 1 . If there is no current, check circuit and repair as
necessary. Make sure that switch has a good ground through wire
connected to "G" terminal.
2) With a good ground circuit and ignition switch in "ON"
position, current should be present at "L" terminal. If there is no
current, replace control switch.
Fig. 1: Jeep Control Switch Terminals
3) On Grand Wagoneer models, turn ignition switch to "ON"
position and press defogger switch. Separate wiring harness at
connector under dash. Connect a 12-volt test light from Purple wire to

Fig. 2: Exploded View of Split Case (4-Pinion)
2) Drive vehicle over formica board until one rear wheel is
in the center of board and paper. Place a block of wood 2" high and a
minimum of 3" wide in front of one of the front wheels.
3) Open throttle gradually attempting to slowly drive vehicle
over block of wood. If paper slips out of position, reposition paper
and repeat test. If vehicle drives over block of wood, axle is
functioning properly.
DANA 4-PINION POWER-LOK
1) With engine off and transmission in "N", raise one wheel
off ground. Block both front and rear wheels of opposite side. Install
adapter tool across 2 wheel studs and attach torque wrench to center
of tool.
2) Observe torque required to continuously turn wheel
smoothly through several revolutions. Repeat test for opposite side.
If differential is okay, torque should be 40-200 ft. lbs. (54-272 N.
m). Disregard breakaway torque. Use rotating torque only.
NOTE: Exploded view of Chrysler Motors Trac-Lok differential was
not available from manufacturer.
REMOVAL & INSTALLATION
See DANA SEMI-FLOATING or FULL-FLOATING AXLE article in this
section.
OVERHAUL
DANA 2-PINION TRAC-LOK
NOTE: For front axle shaft and bearing removal, see articles on
DANA FULL-FLOATING AXLES or 4WD STEERING KNUCKLES in this
section. With the exception of ring gear and differential
side bearings, Chrysler Motors does not recommend disassembly
of differential. If repair is required, manufacturer
recommends replacing entire unit as an assembly.
Disassembly (Jeep)
1) Using 2 screwdrivers, remove pinion snap rings. Using a
brass drift and a hammer, remove pinion shaft from case. Install Step

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DO OR L O CKS - P O W ER

1988 J e ep C hero ke e
1988 Power Door Locks
JEEP
DESCRIPTION
Jeep vehicles with power door locks use a motor-actuated lock
system, controlled by rocker switches. Operation of switch assembly
controls the actuator motor.
Power door locks are protected by a 30-amp circuit breaker
located in the fuse block. Power door locks will not operate from
outside the vehicle.
TESTING
SWITCH
Using ohmmeter, test switches for continuity. Connect
ohmmeter across terminals as shown. See Fig. 1. Continuity should
exist between terminals in all positions.
Fig. 1: Checking Switch Continuity
Courtesy of Chrysler Motors.
ACTUATOR MOTOR
Connect ammeter to actuator motor terminals. Operate door
switch and note reading. Current draw should not exceed 8 amps at room
temperature. Actuator should complete full travel within one second.
Replace actuator motor if not within specification.
CIRCUIT BREAKER
1) Disconnect harness connector from fuse block. Using test
light, check fuse block harness connection for voltage. If there is no
battery voltage at connection, check for burnt fusible link in engine
compartment.
2) Check circuit breaker continuity if voltage exists. Using
ohmmeter, test circuit breaker for continuity. Replace circuit breaker
if no continuity exists.
3) If circuit breaker tests okay, check for battery voltage
at circuit breaker connection of fuse block with wiring harness
installed. If voltage exists at wiring harness but not at circuit
breaker connection, check fuse block for damage.
REMOVAL & INSTALLATION

DOOR LOCK SWITCH
Disconnect battery negative cable. Remove door trim panel.
Remove switch housing from inner door panel. Pry wiring retaining
clips upward while disconnecting wiring. Depress retainer clips
through holes in switch housing. Remove switch assembly. To install,
reverse removal procedure.
ACTUATOR MOTOR
1) Disconnect battery negative cable. Remove door trim panel.
Drill out actuator motor retaining rivets using a 1/4" drill bit.
2) Disconnect actuator rod from bellcrank. Disconnect wires
from actuator motor, and remove motor. To install, reverse removal
procedure, using new rivets.

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DRIV E A XLE - F U LL F LO ATIN G

1988 J e ep C hero ke e
Drive Axles - Dana Full-Floating Axles
Jeep Front & Rear Drive Axles
DESCRIPTION
The axle assembly is an integral carrier type with hypoid
gear ring and pinion. Stamped steel cover is removable for inspection
and repair of differential. Vehicle loads are carried by axle
housings. Axle shafts of "full-floating" rear assemblies may be
removed without disturbing wheel bearings.
Drive pinion depth, pinion bearing preload and differential
side bearing preload are all set by shims.
See LOCKING HUB and 4WD STEERING KNUCKLE articles in this
section for removal and installation procedures for these front drive
axle component parts.
AXLE RATIO & IDENTIFICATION
A metal tag on axle is stamped with gear ratio, part numbers
and limited slip identification. To determine drive axle ratio, refer
to MODEL IDENTIFICATION BY RING GEAR SIZE table.
MODEL IDENTIFICATION BY RING GEAR SIZE









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Model Ring Gear Diameter
44 ....................................... 8.50"
60 ....................................... 9.75"
61 ....................................... 9.75"
70 ...................................... 10.50"
80 ...................................... 11.25"









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FRONT HUB, BEARING, SPINDLE & AXLE SHAFT R & I
FRONT HUB BEARING ADJUSTING SPECIFICATIONS








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Application ( 1) Ft. Lbs. (N.m)
Adjusting Nut
Step 1 ............................... 50 (68)
Step 2 .......................... Back Off 20

Lock Nut ............................... 50 (68)
( 1) - While Rotating Hub.









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REMOVAL (CHEROKEE, COMANCHE & WAGONEER)
1) Raise and support vehicle. Remove tire and wheel assembly.
Remove disc brake caliper and support out of way.
2) Match mark disc rotor and hub and remove disc rotor.
Remove cotter pin, nut lock and axle hub nut. Remove hub-to-knuckle
bolts. Pull hub assembly off axle shaft. Pull axle shaft through
knuckle to remove. Inspect axle shaft "U" joint and shaft splines for
wear. Replace as necessary.
3) Press hub out of bearings. Remove seals and bearings.

1) Coat intermediate shaft with lubricant and carefully slide
through seal and engage in drive axle splines. Install retaining clip.
2) Install shift collar on axle shaft. Install outer axle
shaft and check for smooth operation of shift collar.
3) Apply bead of silicone sealer to inspection cover and
install cover. Fill axle housing with 2.5 pts. (1.2L) of 75W 90 gear
oil. Pour a small amount of gear oil on shift collar and install
disconnect housing. Ensure shifting fork is properly positioned in
shift collar.
4) To complete installation, reverse removal procedure.
Tighten all bolts and nuts to specification. See TORQUE SPECIFICATIONS
table at end of this article.
FRONT AXLE ASSEMBLY R & I
REMOVAL (CHEROKEE, COMANCHE, WAGONEER)
1) Raise and support vehicle. Remove tire and wheel assembly.
Remove hubs, spindles and axles. See FRONT HUB, BEARING, SPINDLE &
AXLE SHAFT in this article.
2) Disconnect vacuum hoses and electrical connections from
shift motor. Disconnect stabilizer bar, track bar and steering damper.
3) Disconnect drive shaft at pinion yoke and tie to frame.
Remove left and right tie rod ends from knuckles.
4) Support axle assembly on floor jack. Remove lower shock
mounts. Disconnect axle housing-to-frame control arms at axle. Lower
floor jack slowly and remove axle assembly. Remove coil spring lower
bracket and coil spring.
INSTALLATION
1) Place axle housing on floor jack and position under
vehicle. Install coil springs and raise assembly into position. Ensure
top of coil springs seat in spring pocket.
2) Check all bushings and mounting hardware for wear or
damage. To complete installation, reverse removal procedure. Tighten
all bolts and nuts to specification. See TORQUE SPECIFICATIONS table
at end of this article. Fill axle assembly with gear oil. Check wheel
alignment.
REAR HUB, BEARINGS & AXLE SHAFTS R & I
1) Raise and support vehicle. Remove tire and wheel assembly.
Remove axle flange nuts or bolts. If nuts are used, rap center of axle
flange sharply with hammer to loosen tapered dowels. Remove bolts or
dowels and pull axle shaft out of hub.
2) Depending on application, bend back ears of lock washer,
or remove locking wedge from nut, or remove snap ring and key. Remove
bearing adjusting nut(s) and remove hub assembly.
3) Remove inner hub seal and bearing. Inspect bearings and
races for wear. To replace bearing, drive outer race from bearing hub
using a punch and hammer. Install new race being careful not to chip
or dent race. Ensure new race is seated in hub.
4) Pack bearings with multi-purpose grease. Install new seal.
Carefully install hub on axle spindle to avoid damaging seal lip and
spindle threads.
5) Install outer bearing and adjusting nut. Tighten bearing
adjusting nut in steps. See REAR HUB BEARING ADJUSTING SPECIFICATIONS
table. Install lock ring if used. Install spindle lock nut if used and
tighten to proper specification. See REAR HUB BEARING ADJUSTING
SPECIFICATIONS table.